Engine piston



Sept. 4, 1923. 1 1,467,257

7 J. THOMSON ENGINE PISTON Filed Aug. 29, 1922 2 Sheets-Sheet l 22- M as 7 1 v\ 7 1h yenior: aa 6? 28 (A I I xmdx f n H 2 I a a Sept. 4, 1923. 1,467,257

J. THOMSON ENGINE PISTON Fild Aug. 29, 1922 2 Sheets-Sheet 2 15 ficiency of engine-pistons and their cylinprobably the least of any non-fluid sub- Pate nted Sept. 4, 19 23. I

UNITED STATES PATENT mm,

some rnomson, or naoonyiq, new roam ENGINE rrsron; Application fled Aughst 2a, 192;. Serial No. 585,022.

To all whom it may concern: be understood as referring, in general terms, 55' Be it known that I, JOHN THOMSON, a to various monolithic and solidified forms citizen of the United States, and a resident and mixtures. of the borough of Brooklyn, city and State Although an academic statement, it may 5 of New York, have invented an Engine be here mentioned thatthe functioning of Piston, of which the following is a specifigraphite as a lubricant, in the forms de- 60 ti I scribed, proceeds about as follows: Molec- This invention relates to reciprocating enular-like-particles are firstly ripped off, or gine-pistons, and is comprised in improvetorn, from the contacting surface and are ments whose dominant objects are to effect then transferred into the microscopic pores an enduring, tight seal against the actuating and hollows of the co-ordinating metal; 65 pressure, as of gas or steam; to largely, or whereby, once a balance is established, the even wholly, avoid the use of oil as a lubrisliding surfaces in fact become graphite'-0n' cant; and to substantially enhance the efgraphlte, whose co-eflicient of friction is ders. Various correlated improvements and stance.

advantages will hereinafter be pointed out. In the drawings, which constitute a part The essence hereof may be thus briefly of this specification,

summated: such a utilization of monolithic Figure 1 is an elevation of the piston degraphite, and of solidified carbon-graphite, picting an effective embodiment of the inin the form of sleeves or tubes combined vention;

with metal, whereby the graphite, when Figure 2 is an end view, developed from cool, will traverse the engine-cylinder com- Figure 1, looking into the interior of the paratively free; but, when heated by the gas piston; K

26 or steam, it will be expanded into a closer Figure 3 is a vertical center section of the and more enduring physical contact with the piston and its connecting rod pin-bracket, as cylinder-wall than would be possible in the on the line A of Figure 2; case of a metal-to-metal contact. Figure 4 is a transverse section, as on the As above employed, the term monolithic lines B, or B of Figure 3;

30 graphite relates to amorphous carbon Figure 5 is a detached, end elevation of 4 which has been graphitized in an electric the aforesaid pin-bracket; i 85 furnace, as by the process of Acheson. As Figure 6 is a broken vertical center secthus produced, it is nearly perfectly pure tion showing the bracket and pin in place in that all of the primary binding material and also depicting a detail modification in has been volatilized; as a lubricant, it stands construction;

second only to oil; and, although this fact is Figure 7 is a half-elevation and a. halfso not generally known, it is considerably comvertical section of a graphite sleeve in its pressible and highly resilient. The term primary form;

carbon-graphite includes artificial or Figure 8 is a transverse section, as along 40 natural graphite, or amorphous carbon, in the lines C, or C of Figure 7;

the form of powder, dust or flakes, with Figure 9 is a half vertical center section which is mixed some modicum of binding and a half elevation of a piston in the material, such as the kaolins, sodium silicate, rough, prior to being machined to its. fin: bitumen or the like; and, when plastic, is ished dimensions, denoted by the broken 45 molded or extruded to the desired form and lines D, D;

thenafter baked in kilns. The lubricating Figure 10 is a half end view and a half uality of carbon-graphite does not equal transverse section, the latter taken as along t at of the electrically graphitized product; the lines E or E of Figure 9; and but, in various cases, it has compensating Figure 11 denotes a detail modification in.

5 features, such as being denser, more resistthe construction over that of Figuresfand 8.

ant to shockand is readilv inexpensively The drawings are approximately full ice moldable in metal dies with a close apscale reproductions of designs reduced to proximation to accuracy. Therefore, when practice, as applied to a Buick automobile. the term, graphite, is hereinafterused it is to It should be borne mind that to efiecsleeve is deemed wise, the cylindrical metal towards the center,

being due to the wedgedenote the final piston, I

ished; the primary advantage of which is tively withstand the explosive shocks, high speed of action and the rapid and extreme changes in temperature imparted to, say, a gas engine -piston, the graphite must be applied with the very utmost rigidity pos sible to attain; and, as the tensile strength of graphite, or of carbon-graphite, is low whilst its crushing resistance is relatively high, the one best way of attaining the desired end is to utilize the graphite in such manner that it shall be largely held and gripped under compression; which is so appliedas not to also produce other than nominal tensile stresses.

The employment of a single graphite a highly effective mode of realizing the benefits of this invention, in that the greatest area of bearing surface is thereby afi'orded and but one such member has to be dealt with. Thus, the sleeve 25, in itsprimary form, as see Figure 7, does not require, at this stage of the maneuvre, to be finished with accuracy. If formed by machining it from a solid round rod, or if extruded, or if molded, it is then provided with a plurality of transverse slots, as 26, preferably cut by a circular saw, indicated by the dotted outline 27, Figure 8, which 18 sunk into and through the sleeve from its exterior surface; and whilst the inner length of each of the slots, as notated, may be 1 inch, the outer length may be 1% inch. This slotted sleeve is then placed in an ordinary green sand mold, as in the case of a baked sand core, which co-ordinates with a suitable pattern of the desired piston, when molten metal is run into the mold-cavity. In this portion M, and the enclosing head N, are formed; and the aforesaid slots are filled with molten metal, as 28, which, when solidified, sub]ects the graphite to the utmost degree of compression that the shrinkage of the metal from the molten to the solid state is capable of imparting, vertically between the sides of the metal, as J in Figure 9, and also radially, as P in Figure 10, this secondary action shaped interlock the graphite.-

The dotted lines,

of the metal in the slots of D, D Figures 9 and 10 ing, or as is shown in the completed form of Fi res 1, 2, 3 and 4. e

will be perceived by inspection of the aforesaid figures, the entiresurface of the outside and inside, is machine finthat the cylindrical metal portion may be much thinner and lighter than would otherwise be ossible; but, as a correlative there: to, the ubs in which the connecting rod pin is mounted must be separately applied. This is accomplished by forming the hubs 30, 31, upon. extensions, 32, 33, rising from piston.

finished contour in the castreams? a circular base, 34. The outer hub-surfaces, as 35, Figure 5, are finished to the circular contour of the inner wall of the piston, and a threaded bore, 37, in the base is adapted to a threaded hub, 38, on the piston-head. In this wise, the base of the pin-bracket can be forced into very intimate contact with the piston-head; which can be made thinner than ordinarily, as the circular base of the bracket serves as a reinforcement. When the bracket is thus secured, the bearing for the connecting rod pin is drilled through the piston and the bracket-bosses and when the pin itself, as 39, is inserted, the impelling thrust is largely imparted thereto directly from the iston-head and also, but to a considerabl esser extent, from the piston-wall.

In some cases, the connecting rod rocks on the pin, in other cases the pin rocks in the When the latter is practiced the bearing quality of hubs may not be, and usually is not, of first grade for the onerous duty performed. But by means of this separate pin-bracket'it is then feasible to form it of the most enduring material possible to utilize.

In a gas engine, the temperature imparted to and retained by the piston is substantially higher than that of the containing cylinder; and the enclosed head of the piston will be maintained at a higher temperature than its open or skirt-portion. Consequently, and dependent upon the co-efficient of expansion and contraction of the material used, the diameter, or diameters, of the piston will be less, when it is cold, by some thousandths of an inch, than the bore of the cylinder. Therefore, the prevailing practice is to so adapt the diameters that the. piston, when heated, shall be closely contiguous to but not in intense physical contact with the c linder-wall; for, whatever may be the combination of metals, if the piston is so expanded as not to afford oil-space, it is bound to out, score or freeze. Per contra, when the material of the piston which is expanded to than it ought to be, the graphite acts to I clear itself. A most important contingent advantage is here derived, namely: As the graphite is self-lubricating, and as it can be fitted more closely than in the case of metal, oil is kept out of the explosion chamber and the formation of hydro-carbon therein is diminished to a minimum, or even wholly avoided.

When the graphite isfinished to the exact diameter required, the diameters of the obtruding metal segments are reduced, by forming circular recesses, as 40, Figures 1, 3 and 4, whereby to prevent any metallic contact with the cylinder; moreover, this operof I contact with ooves, leakage ciency is aided by applying an ordinary split metal packing ring, as 41, preferably disposed in a recess near the head of the piston, whose particular function is to temporarily hold the initial compression when the piston is cold. As this ring traverses the highly polished and graphited surface of the cylinder, the condition of the operation is much more favorable for long endurance than in existing practice. If desired, the split ring may be mounted in the graphite, asis shown in Figure 6. 1

As previously mentioned, monolithic graphite is compressible and resilient.

These functions are aids to the 'success of this system; for, if the graphite is driven by heat-expansion into an excessive intimacy the cylinder, it will compress, but, due to its resiliency, a permanent set does not ensue.

Various detail modifications may be made according to the wishes of users or designers.

in the sleeve,

*the perimeters. of said portions being For example, instead of forming the slots they may be substituted by numerous drilled holes, preferably ta ring outwardly, as 42, Figure 11, and t e pin bracket may be riveted, or electrically welded, or both, to the piston instead of being attached as shown. 1

What I claim is:

1. Anengine piston formed ofa metallic headed cylinder and an exterior sleeve of solidified graphitic carbon, said sleeve being I provided with a plurality of wedge-like slots primarily filled with molten metal; whereby,

when chilled, the graphitic sleeve is compressed vertically and radially.

2. An en e piston formed ofan'exterior tube of solidified graphitic carbon and an inner metallic cylinder in which portions of the metal extend through the graphitic tube,

reduced to diameters lesser than that of the coordinating surface of the engine-cylinder.

This specification signed on this the 28th,

day of August,\A. D.,1922.

JOHN THOMSON.- 

